Water content of a part of object evaluation method and water content of a part of object evaluation apparatus

ABSTRACT

A water content evaluation apparatus which evaluates water content of a part of an object is provided. A water content at each of irradiation positions of the part of the object is calculated based on a first reflection light of a laser reference beam, having a first wavelength that is not absorbed by water, that is reflected at all the irradiation positions of the object and a second reflection light of a laser measuring beam, having a second wavelength that is absorbed by water, that is reflected at all the irradiation positions of the object. Irradiation positions of the object in which the water content is equal to or larger than at least one predetermined threshold level are output.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. patent application Ser. No.16/155,357, filed Oct. 9, 2018, which is a continuation application ofU.S. patent application Ser. No. 15/295,065, filed Oct. 17, 2016 and nowU.S. Pat. No. 10,126,234, which claims the benefit of Japanese PatentApplication Nos. 2015-209231, filed on Oct. 23, 2015, and 2015-209230,filed on Oct. 23, 2015. The entire disclosure of each of theabove-identified applications, including the specification, drawings,and claims, is incorporated herein by reference in its entirety.

BACKGROUND 1. Field of the Invention

The present disclosure relates to a water content evaluation method anda water content evaluation apparatus which measures water contentcontained in a leaf or a part of plant.

2. Description of the Related Art

There is a potential difference inside and outside of a cell in a normalplant and electromotive force is generated. It is possible to describe amechanism which generates such electromotive force based on, forexample, an electrophysiological model of an axial organ of a higherplant. In particular, various methods are suggested in which a state ofa root of the plant (for example, water stress) is examinednon-destructively utilizing electromotive force between the root andsoil.

As a technique in which water stress in a plant is measured utilizingthe method described above, for example, JP-A-2001-272373 disclosesconnecting a first nonpolarizable electrode to the plant, connecting asecond nonpolarizable electrode to soil in which the plant is planted,providing a potentiometer between the two nonpolarizable electrodes, andbeing able to measure water stress which is received by the plant bymeasuring electromotive force between both nonpolarizable electrodesusing the potentiometer.

In a case where water content that is contained in a leaf is measured byirradiating the leaf of the plant with a near infrared beam and statusof the plant is evaluated, the configuration in PTL 1 has the followingproblem. The leaf of the plant performs movement such as contraction bybending or coiling, and opening or closing in the morning, in theafternoon, and in the evening, daily or in increments of time.

In a case where water content is measured which is contained in the leafby irradiating the leaf of the plant with the near infrared beam andstatus of the plant is evaluated, the leaf of the plant performsmovement such as contraction by bending or coiling, and opening orclosing in the morning, in the afternoon, and in the evening, daily orin increments of time. Thickness of the leaf changes in an optical axisdirection according to the movement of the leaf. For example, when angleθ is inclined to the front due to the leaf that stands in a verticaldirection with respect to the optical axis bending, the thickness of theleaf in the optical axis direction is raised by (1/cos θ). The increasein the thickness is obtained by a measurement result in which the watercontent that is contained in the leaf is greater than in reality. Inaddition, when measuring by irradiating a front surface of the leaf withthe near infrared beam at a predetermined spot diameter, the leaf isdamaged from a portion of an irradiation range due to movement of theleaf, an irradiation area (projection area) of the leaf is small, andthe measurement result is obtained in which the water content is lowerthan in reality.

In this manner, an error may be generated in measurement precision ofthe water content of the leaf, and it may not be possible to correctlyevaluate status of the plant since accurate water content is notobtained.

In addition, the leaves of a seedling in a field grow in abundance andare foliage. In the foliage, a plurality of leaves overlap is respectiveorientations, and for example, when wind blows, the leaves relativelymove.

Since the water content which is contained in the leaf is measured byirradiating the leaf of the plant with the near infrared beam and statusof the plant is evaluated, in a case where the front surface of the leafof the plant is irradiated with two types of near infrared beams andwater content is obtained from a reflection intensity rate therefrom,the radiated near infrared beam is absorbed and scattered due to theleaf on a periphery of a leaf that is a measurement target (refer toFIG. 21A). Other than, for example, the radiated near infrared beambeing absorbed by the leaf that is the measurement target, a leaf on theleft side is also radiated and a portion is absorbed. The leaf on theleft side is radiated, and the near infrared beam that is scattered bythe leaf on the left side is diffused on the leaf that is themeasurement target. In addition, multiple scattering also occurs inwhich a leaf on the right side is radiated, and diffused light that isscattered by the leaf on the right side is diffused to another leaf andis diffused on the leaf that is the measurement target. Since thebackground of the reflection intensity rate that is obtained bymeasurement is significantly raised, the multiple scattering isdifficult to distinguish individually to the leaf that is themeasurement target and the leaves on the periphery of the measurementtarget. In addition, the plurality of leaves overlap or are separated,and a target area of the leaf on which the near infrared beam isradiated changes (refer to FIG. 21B).

Accordingly, even in measurement of presence or absence of watercontent, individual leaves on the periphery and the target leaf aredifficult to distinguish.

SUMMARY

The present disclosure has an object of accurately measuring watercontent which is contained in a measurement target such as a leaf or apart of plant.

Furthermore, the present disclosure has an object of eliminatinginfluence due to scattered light (light scattered externally) from aperipheral leaf and accurately measuring water content of the leaf orthe part of plant that is the measurement target even within foliage inwhich multiple leaves grow in abundance.

According to an aspect of the present disclosure, there is provided awater content evaluation apparatus including a first light source whichradiates a near infrared laser reference beam of a first wavelength thathas a characteristic in which light tends not to be absorbed in waterwhile sequentially scanning toward a plant, a second light source whichradiates a near infrared laser measuring beam of a second wavelengththat has a characteristic in which light tends to be absorbed in waterwhile sequentially scanning toward the plant, and a water contentcalculation unit which calculates water content at all irradiationpositions of the plant based on a reflection light of the near infraredlaser reference beam that is reflected on all irradiation positions ofthe plant and a reflection light of the near infrared laser measuringbeam that is reflected on all irradiation positions of the plant.

According to another aspect of the present disclosure, there is provideda water content evaluation apparatus including a first light sourcewhich radiates a near infrared laser reference beam of a firstwavelength that has a characteristic in which light tends not to beabsorbed in water while sequentially scanning toward an irradiation areawhich includes a background material that covers a back surface of apart of the water content evaluation apparatus that is set as anevaluation target and a part of the plant that is set as an evaluationtarget, a second light source which radiates a near infrared lasermeasuring beam of a second wavelength that has a characteristic in whichlight tends to be absorbed in water while sequentially scanning towardthe irradiation area, an identification unit which identifies the partof the irradiation area that is the evaluation target based on areflection light of the near infrared laser reference beam that isreflected on the irradiation area and a reflection light of the nearinfrared laser measuring beam that is reflected on the irradiation area,and a water content calculation unit which calculates water content inthe part that is the evaluation target which is identified by theidentification unit.

According to still another aspect of the present disclosure, there isprovided a water content evaluation method in the water contentevaluation apparatus, the method including: causing a first light sourceto radiate a near infrared laser reference beam of a first wavelengththat has a characteristic in which light tends not to be absorbed inwater while sequentially scanning toward a plant; causing a second lightsource to radiate a near infrared laser measuring beam of a secondwavelength that has a characteristic in which light tends to be absorbedin water while sequentially scanning toward the plant; and calculatingwater content at all irradiation positions of the plant based on areflection light of the near infrared laser reference beam that isreflected on all irradiation positions of the plant and a reflectionlight of the near infrared laser measuring beam that is reflected on allirradiation positions of the part of the plant.

According to still another aspect of the present disclosure, there isprovided a water content evaluation method in the water contentevaluation apparatus which evaluates water content of a part of a plant,the method including: disposing a background material which covers aback surface of a part of the plant that is set as an evaluation targetof the water content evaluation apparatus; causing a first light sourceto radiate a near infrared laser reference beam of a first wavelengththat has a characteristic in which light tends not to be absorbed inwater while sequentially scanning toward an irradiation area whichincludes the part that is set as the evaluation target and a backgroundmaterial; causing a second light source to radiate a near infrared lasermeasuring beam of a second wavelength that has a characteristic in whichlight tends to be absorbed in water while sequentially scanning towardthe irradiation area, and identifying the part of the irradiation areathat is set as the evaluation target based on a reflection light of thenear infrared laser reference beam that is reflected on the irradiationarea and a reflection light of the near infrared laser measuring beamthat is reflected on the irradiation area to calculate water content inthe part that is the evaluation target.

According to the aspects of the present disclosure, it is possible toaccurately measure water content which is contained in the measurementtarget.

Furthermore, according to the aspects of the present disclosure, in acase where the measurement target is, for example, a leaf or a part ofplant, it is possible to eliminate influence due to scattered light(light scattered externally) from the peripheral leaf and accuratelymeasure the water content of the leaf or the part of the plant that isthe measurement target even within the foliage in which multiple leavesgrow in abundance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual explanatory diagram illustrating an example ofusage circumstances of a detection camera in a first embodiment;

FIG. 2 is a block diagram illustrating in detail an example of aninternal configuration of the detection camera;

FIG. 3 is a diagram illustrating in detail an example of an internalconfiguration of a determiner of the detection camera;

FIG. 4 is a flow chart illustrating an example of an initial operationin a controller of the detection camera;

FIG. 5 is a principle explanatory diagram of detection of water in aninvisible light sensor;

FIG. 6 is a graph illustrating a near infrared spectra of water (H₂O);

FIG. 7A is a diagram which describes a summary of an operation whichmeasures a reflection intensity rate of the entirety of a leaf;

FIG. 7B is a diagram which describes a summary of an operation thatmeasures the reflection intensity rate in which a spot is in a fixedarea;

FIG. 8 is a flow chart illustrating a detailed operation procedure whichrelates to detection of water content of a leaf or a part of plant inthe invisible light sensor;

FIG. 9 is a flow chart illustrating a calculation procedure of a watercontent index in step S18-5;

FIG. 10 is a table illustrating a tone color corresponding to thereflection intensity rate;

FIG. 11 is a table illustrating the reflection intensity rate in aportion of a frame image which includes a pixel space that the leafoccupies;

FIG. 12A is a frame image that images stalks and leaves of a tomato;

FIG. 12B is a diagram illustrating an occupancy space of the leaf thatis obtained in a case where an imaging distance is set to 3 m and athreshold level is set to 0.05 with respect to the visible light imageof FIG. 12A;

FIG. 12C is a diagram illustrating an occupancy space of the leaf whichis obtained in a case where the imaging distance is set to 1 m and thethreshold level is set to 0.3 with respect to the visible light image ofFIG. 12A;

FIG. 13 is a flow chart illustrating a threshold level settingprocedure;

FIG. 14 is a graph illustrating a frequency distribution of thereflection intensity rate in all pixels;

FIG. 15A is a diagram illustrating the leaf that is fixed in variouspostures during measurement;

FIG. 15:13 is a diagram illustrating an image which represents thereflection intensity rate of the leaf;

FIG. 16 is a graph illustrating the reflection intensity rate withrespect to average content;

FIG. 17A is a graph illustrating a wilting process of the plant;

FIG. 17B is a graph illustrating a revival process;

FIG. 18 is a diagram illustrating a process in which water content ofthe leaf that approaches wilting gradually increases;

FIG. 19 is a diagram which describes a measurement method of acomparative example;

FIG. 20A is a graph illustrating a time change of weight of the leaf dueto transpiration, that is, a time change of average water content of theleaf;

FIG. 20B is a graph illustrating a time change of reflection intensityrate Ln (I905/I1550) that is measured at 12 locations on the leaf;

FIG. 20C is a graph which is obtained based on measurement data of FIGS.20A and 20B, and illustrating a correspondence relationship ofreflection intensity rate Ln (I905/I1550) and the average water content;

FIG. 21A is a diagram which describes a summary of an operation of awater content evaluation apparatus in a second embodiment;

FIG. 21B is a diagram illustrating overlapping of leaves;

FIG. 22A is a graph illustrating a reflection light intensity withrespect to a wavelength of a near infrared beam when near infrared beamis radiated toward the leaf outdoors;

FIG. 22B is a graph illustrating a reflection light intensity withrespect to a wavelength of the near infrared beam when the near infraredbeam is radiated toward the leaf on which a white reference substrate isinstalled indoors and outdoors;

FIG. 23 is a diagram which describes attachment of the leaf on the whitereference substrate;

FIG. 24 is a diagram illustrating various installation methods of thewhite reference substrate that is installed so as to cover the backsurface of the leaf that is a measurement target;

FIG. 25A is a photo illustrating the leaf that is the measurement targetof water content outside;

FIG. 25B is a diagram illustrating reflection intensity rate Ln(I905/I1550) of the leaf;

FIG. 25C is a diagram illustrating reflection intensity rate Ln(I905/I1550) of the leaf;

FIG. 26A is a table illustrating the reflection intensity rate in aportion of a frame image which includes a pixel space that the leafoccupies which is covered by the back surface on the white referencesubstrate;

FIG. 26B is a table illustrating the reflection intensity rate in aportion of the frame image which includes the pixel space that the leafoccupies which is not covered by the back surface on the white referencesubstrate;

FIG. 27 is a photo illustrating the leaf that is the measurement targetof half of the water content outside;

FIG. 28A is a graph illustrating the time change of the water contentindex of the leaf in a first half measurement and the leaf in a secondhalf measurement;

FIG. 28B is a graph illustrating the time change of the water contentindex of the leaf in a third half measurement; and

FIG. 28C is a graph illustrating the time change of the water contentindex of foliage in a fourth half measurement.

DETAILED DESCRIPTION Details and Problems of First Embodiment

As a method for obtaining water content of a leaf or a part of a plantremotely without breaking the leaf, the present inventor and the likesuggests a method of irradiating the front surface of the leaf with twotypes of near infrared beams and obtaining water from the reflectionintensity rate. One near infrared beam out of the two types of nearinfrared beams is a laser beam which has, for example, a wavelength of905 nm, and is used as a reference beam which is transmitted throughwater. The other near infrared beam is the laser beam which has, forexample, a wavelength of 1550 nm, and is used as a measuring beam whichis absorbed in water. The reference beam and the measuring beam areradiated two times on the front surface of the leaf; and the reflectionlight is received by an invisible light camera. Light is received by theinvisible light camera, and reflection intensity rate Ln (I905/I1550)which is a reflection intensity rate of the reference beam andreflection intensity of the measuring beam is a value which isequivalent to water content at an irradiation position.

As shown in FIG. 7B, a laser beam is radiated within a range of a spotdiameter (for example, 20 mmφ) smaller than the front surface of leafPT3 while sequentially scanning, and an average surface reflectionintensity rate is obtained in spot sp1. Water content per unit area ispresumed from the average surface reflection intensity rate. However, itis already known that correlation between water content per unit areaand water potential is low (refer to as follows: “NondestructiveInstrumentation of Water-stressed Cucumber Leaves” Comparison betweenChanges in Spectral Reflectance, Stomatal. Conductance, PSII Yield andShape The University of Tokyo, Graduate School of Agricultural and LifeSciences, Agricultural Information Research, Vol. 11 (2002), No. 2, p.161-170). Water potential is a value which represents water retentioncapability (water content) of the plant, and is an index which measuresstatus (in other words, degree of health) of the plant.

The shape of the leaf is not fixed to a key factor of the correlationbetween water content per unit area and water potential being low, andis considered to change according to wilting, bending, coiling, and thelike. The leaf of the plant performs movement by bending or coiling andopening or closing (contracting) in the morning, in the afternoon, andin the evening, daily or in increments of time.

In a case where water content is measured by radiating the near infraredbeam, thickness of the leaf changes in an optical axis directionaccording to the movement of the leaf. For example, when angle θ isinclined to the front due to leaf PT3 that stands in a verticaldirection with respect to the optical axis bending, the thickness of theleaf in the optical axis direction is raised by (1/cos θ). The increasein the thickness is obtained by a measurement result in which the watercontent that is contained in leaf PT3 is greater than in reality. Inaddition, when measuring by irradiating a front surface of the leaf withthe near infrared beam at a predetermined spot diameter, leaf PT3 isdamaged from portion vp1 of an irradiation range due to movement of theleaf, an irradiation area (projection area) of the leaf is small, andthe measurement result is obtained in which the water content is lowerthan in reality.

Accordingly, even if the near infrared beam (laser beam) is radiated inthe spot, and the water content per unit time of the leaf is measured,status of the leaf cannot be understood well.

Therefore, in the first embodiment, it is possible to accurately measurewater content which is contained in the plant that is the index ofstatus of the plant.

First Embodiment

A first embodiment, which specifically exemplifies the water contentevaluation apparatus and the water content evaluation method accordingto the present disclosure, will be described in detail with reference tothe accompanying drawings. However, detailed description may be omittedas necessary. For example, detailed description of already well-knownmatter and overlapping description with respect to substantially thesame configuration may be omitted. This is because the followingdescription is prevented from unnecessarily becoming redundant, and aprocess of the inventor is easily set. Note that, drawings and thefollowing description are provided by the inventor for sufficientunderstanding of the present disclosure, and thereby, the presentdisclosure is not intended to be limited to a subject described in therange of the claims.

Description is made exemplifying detection camera 1 indicated in FIG. 1as an example of the water content evaluation apparatus of the presentembodiment. The present embodiment is able to be expressed as the watercontent evaluation method which executes each process that is performedby the detection camera. Detection camera 1 of the present embodiment isable to detect a distribution state of presence or absence of watercontent of the leaf or the part of the plant.

Here, an observation target of detection camera 1 of the presentembodiment is the leaf or the part of the plant, and description is madeby exemplifying a fruit vegetable that is given as a more specificexample. Since sugar content of a fruit of a tomato is increased ingrowth of fruit vegetables such as, for example, the tomato, it is knownthat it is necessary for water or fertilizer to be in an insufficientstate and not a state in which water or fertilizer is sufficientlysupplied as a result of water or fertilizer of a root or a leaf beingdigested by a suitable amount in photosynthesis. For example, ifsufficient water is supplied to the leaf, the leaf has a flat shape in asound state. Meanwhile, when water of the leaf is equivalentlyinsufficient, the shape of the leaf is bent. Meanwhile, when fertilizerin the soil is equivalently insufficient, a condition is generated ofthe leaf turning yellow and the like.

In the present embodiment below, an example is described in whichdetection camera 1 radiates laser beams of a plurality of types whichare different in wavelength on the plant (for example leaf), and detectswater content of the leaf based on an intensity rate of respectivediffuse reflection light that are reflected on irradiation positions ofthe leaf. Note that, in the present embodiment, the leaf of the plant isthe measurement target, but the measurement target is not limited to theleaf, and may be other parts of a seed, stalk, flower, and the like. Asecond embodiment is also the same.

Outline of Detection Camera

FIG. 1 is a conceptual explanatory diagram illustrating an example ofusage circumstances of detection camera 1 in the first embodiment.Detection camera 1 is installed at a fixed point within a plasticgreenhouse in which, for example, fruit vegetables such as the tomatoare planted. In detail, for example, detection camera 1 is installed onbase BS that is fixed to mounting jig ZG which is attached so as tointerpose support column MT1 with a cylindrical shape extend in avertical direction from the ground. Detection camera 1 operates by apower source to be supplied from power source switch PWS that isattached to support column MT1, and radiates reference beam LS1 andmeasuring beam LS2 that are a plurality of types of laser beams whichhave different wavelengths toward plant PT that is the observationtarget across irradiation range RNG.

Plant PT is, for example, a fruit vegetable plant such as the tomato, aroot of plant PT which grows from soil SL that is filled in soil pot SLPwhich is installed on base BB, and plant PT has each of stem PT1, stalkPT2, leaf PT3, fruit PT4, and flower PT5. Fertilizer water supply deviceWF is installed on base BB. Fertilizer water supply device WF supplieswater to soil spot SLP via, for example, cable WL according to aninstruction from wireless communication system RFSY that is connectedvia local area network (LAN) cable LCB2. Thereby, since water issupplied to soil SL, the root of plant PT absorbs water, and transmitswater to each part within plant PT (that is, stem PT1, stalk PT2, leafPT3, fruit PT4, and flower PT5).

In addition, detection camera 1 receives diffuse reflection light RV1and RV2 that are reflected on an irradiation position of plant PT whichis radiated by reference beam LS1 and measuring beam LS2, andfurthermore, receives ambient light RV0. As will be described later,detection camera 1 has a normal camera function, and is able to image animage (that is, image of plant PT within the plastic greenhouseindicated in FIG. 1) within a default angle of view due to ambient lightRV0 entering. Detection camera 1 outputs output data which includesvarious detection results (refer to description below) or image data todata logger DL based on diffuse reflection light RV1 and RV2.

Data logger DL transmits output data from detection camera 1 tomanagement personal computer (PC) of a control room within an office ata position geographically separated from the plastic greenhouse via LANcable LCB1 and wireless communication system RFSY. Wirelesscommunication system RFSY is not particularly limited in communicationspecification, but controls communication between data logger DL withinthe plastic greenhouse and management PC within the control room in theoffice, and furthermore transmits an instruction from management PCwhich relates to supply of water or fertilizer of soil spot SLP tofertilizer water supply device WF.

Monitor 50 is connected to management PC within the control room in theoffice, and management PC displays output data of detection camera 1that is transmitted from data logger DL on monitor 50. In FIG. 1, forexample, monitor 50 displays the entirety of plant PT that is themonitoring target and a distribution state which relates to presence orabsence of water in the entirety of plant PT. In addition, monitor 50generates and is able to comparatively display an enlargementdistribution state of a specific designated location out of the entiretyof plant PT (that is, designated location ZM that is specified by a zoomoperation of an observer who uses management PC) and image datacorresponding to the designated location of the enlargement distributionstate.

Detection camera 1 has a configuration which includes visible lightcamera VSC and invisible light sensor NVSS. Visible light camera VSC(acquiring unit) images plant PT within the plastic greenhouse usingambient light RV0 with respect to invisible light that has apredetermined wavelength (for example, 0.4 to 0.7 μm) in the same manneras, for example, existing monitoring camera. Image data of the plantthat is imaged by visible light camera VSC refers to “visible lightcamera image data”.

Invisible light sensor NVSS incidents reference beam LS1 and measuringbeam LS2 which is invisible light (for example, infrared beam) that hasa plurality of types of wavelengths (refer to description below) withrespect to the same plant PT as invisible light sensor VSC. Invisiblelight sensor NVSS detects presence or absence of water at theirradiation position of plant PT which is the monitoring target usingthe intensity rate of diffuse reflection light RV1 and RV2 that arereflected on the irradiation position of plant PT which is radiated byreference beam LS1 and measuring beam LS2.

In addition, in visible light camera image data that is imaged byvisible light camera VSC, detection camera 1 generates and outputsoutput image data (hereinafter referred to as “detection result imagedata”) which is equivalent to the detection result of water of invisiblelight sensor NVSS or display data that composites information whichrelates to detection result image data. Display data is not limited toimage data in which detection result image data and visible light cameraimage data are composited, and for example, may be image data that isgenerated such that detection result image data and visible light cameraimage data are able to be compared. An output destination of the displaydata from detection camera 1 is an externally connected device that isconnected to detection camera 1 via, for example, a network, and is datalogger DL or communication terminal MT (refer to FIG. 2). The networkmay be a wired network (for example, intranet or internet), and may be awireless network (for example, wireless LAN).

Description of Each Part of Detection Camera

FIG. 2 is a block diagram illustrating in detail an example of aninternal configuration of detection camera 1. Detection camera 1 whichis indicated in FIG. 2 has a configuration which includes invisiblelight sensor NVSS and visible light camera VSC. Invisible light sensorNVSS has a configuration which includes controller 11, beam output PJ,and determiner JG. Beam output PJ has first beam source 13, second beamsource 15, and beam scanner 17. Determiner JG has imaging optics 21,photo detector 23, signal processor 25, detection processor 27, anddetection processor 29. Visible light camera VSC has imaging optics 31,photo detector 33, image signal processor 35, and display controller 37.Communication terminal MT is portable by a user (for example, observerof growth of plant PT of fruit vegetable plant such as the tomato,hereinafter the same).

In the description of each part of detection camera 1, controller 11,invisible light sensor NVSS, and visible light sensor VSC are describedin order.

Controller 11 is configured using, for example, a central processor(CPU), a micro processor (MPU), or a digital signal processor (DSP),(and also configured using, for example, a program memory and a workmemory) and performs a signal process for totally controlling anoperation control of each part of visible light sensor VSC and invisiblelight sensor NVSS, an input and output process of data within otherparts, a computing process of data, and a storage process of data. Inaddition, controller 11 includes timing controller 11 a described later(refer to FIG. 3).

Controller 11 sets detection threshold level M of plant PT which is thedetection target of invisible light sensor NVSS to detection processor27 described later. Details of the operation of controller 11 will bedescribed later with reference to FIG. 4.

Timing controller 11 a controls output of first beam source 13 andsecond beam source 15 in beam output PJ. In detail, timing controller 11a outputs timing signal for beam scanning TR to first beam source 13 andsecond beam source 15 in a case where light is incident to first beamsource 13 and second beam source 15.

In addition, during the start of a predetermined incidence period,timing controller 11 a alternately outputs beam output signal RF tofirst beam source 13 and second beam source 15. In detail, during thestart of the incidence period of an odd number of times, timingcontroller 11 a outputs beam output signal RF to first beam source 13and during the start of the incidence period of an even number of times,outputs beam output signal RF to second beam source 15.

Next, each part of invisible light sensor NVSS is described.

When first beam source 13 as an example of the first light sourcereceives timing signal for beam scanning TR from timing controller 11 aof controller 11, reference beam LS1 (for example, near infrared beam)that is a laser beam of invisible light that has a predeterminedwavelength (for example, 905 nm) is incident on plant PT via beamscanner 17 according to beam output signal RF from timing controller 11a in each incidence period (default value) of an odd number of times.

Note that, presence or absence of detection of water in plant PT may bedetermined by comparing to the predetermined detection threshold levelM. Detection threshold level M may be a predetermined value, may be anarbitrarily set value, and furthermore, may be a value based onintensity of the diffuse reflection light that is acquired in a state inwhich there is no water (for example, a value in which a predeterminedmargin is added to a value of intensity of the diffuse reflection lightthat is obtained in a state in which there is no water). That is,presence or absence of detection of water may be determined by comparingdetection result image data that is acquired in a state in which thereis no water and detection result image data that is acquired thereafter.In this manner, it is possible to set a threshold level appropriate foran environment in which detection camera 1 is installed as detectingthreshold level M of presence or absence of water by acquiring intensityof the diffuse reflection light in the state in which there is no water.

When second beam source 15 as an example of the second light sourcereceives timing signal for beam scanning TR from timing controller 11.aof controller 11, measuring beam LS2 (for example, infrared beam) thatis the laser beam of invisible light that has a predetermined wavelength(for example, 1550 nm) is incident on plant PT via beam scanner 17according to beam output signal RF from timing controller 11 a in eachincidence period (default value) of an even number of times. In thepresent embodiment, measuring beam LS2 that is incident from second beamsource 15 is used in determination of presence or absence of detectionof water in plant PT. Wavelength 1550 nm of measuring beam LS2 is awavelength which has a characteristic in which light tends to beabsorbed in water (refer to FIG. 6).

Furthermore, detection camera 1 detects presence or absence of water atthe irradiation position of plant PT that is radiated by reference beamLS1 and measuring beam LS2 using diffuse reflection light RV1 ofreference beam LS1 as reference data for detecting water at theirradiation position of plant PT, and using diffuse reflection light RV2at the irradiation position of plant PT that is radiated by measuringbeam LS2 and diffuse reflection light RV1 of reference beam LS1.Accordingly, detection camera 1 is able to detect water of plant PT withhigh precision using reference beam LS1 and measuring beam LS2 of twotypes of wavelengths that detect water in plant PT differently anddiffuse reflection lights RV1 and RV2 thereof.

Beam scanner 17 two-dimensionally scans reference beam LS1 which isincident from first beam source 13 and measuring beam LS2 which isincident from second beam source 15 with respect to plant PT that ispresent in a detection area in invisible light sensor NVSS. Thereby,detection camera 1 detects presence or absence of water at theirradiation position of plant PT that is radiated by reference beam LS1and measuring beam LS2 based on diffuse reflection light RV2 that isreflected at the irradiation position of plant PT by measuring beam LS2and diffuse reflection light RV1 described above.

Next, an internal configuration of determiner JG is described in detailwith reference to FIGS. 2 and 3. FIG. 3 is a diagram illustrating indetail an example of an internal configuration of a determiner JG ofdetection camera 1.

Imaging optics 21 is configured using, for example, a lens, light (forexample, diffuse reflection light RV1 or diffuse reflection light RV2)which is incident from outside of detection camera 1 is concentrated,and diffuse reflection light RV1 or diffuse reflection light RV2 form animage on a predetermined imaging area of photo detector 23.

Photo detector 23 is an image sensor which has a peak of spectralsensitivity with respect to wavelengths of both of reference beam LS1and measuring beam LS2. Photo detector 23 converts an optical image ofdiffuse reflection light RV1 or diffuse reflection light RV2 that forman image on the imaging area to an electrical signal. Output of photodetector 23 is input to signal processor 25 as the electrical signal(current signal). Note that, imaging optics 21 and photo detector 23functions as an imaging unit in invisible light sensor NVSS.

Signal processor 25 has I/V converter 25 a, amplifier 25 b, andcomparator/peak hold 25 c. I/V converter 25 a converts the currentsignal that is an output signal (analog signal) of photo detector 23 toa voltage signal. Amplifier 25 b amplifies a level of the voltage signalthat is the output signal (analog signal) of I/V converter 25 a up to aprocessable level in comparator/peak hold 25 c.

Comparator/peak hold 25 c binarizes the output signal of amplifier 25 band outputs to threshold level setter/water content index (index ofwater content) detector 27 a according to a comparative result of theoutput signal (analog signal) of amplifier 25 b and the predeterminedthreshold level. In addition, comparator/peak hold 25 c includes ananalog digital converter (ADC), detects and holds the peak of an analogdigital (AD) converter result of the output signal (analog signal) ofamplifier 25 b and furthermore, outputs peak information to thresholdlevel setter/water content index detector 27 a.

Detection processor 27 has threshold level setter/water content indexdetector 27 a, memory 27 b, and detection result filter 27 c. Thresholdlevel setter/water content index detector 27 a (threshold level holder)generates and registers frequency distribution data in advance (refer toFIG. 14). Frequency distribution data indicates frequency distributionof the reflection intensity rate (water content index) in all pixels orone frame image. As will be described later, threshold levelsetter/water content index detector 27 a (threshold level calculationunit) is set by calculating threshold level Sh of the reflectionintensity rate for identifying the shape of the leaf using the frequencydistribution data.

In addition, threshold level setter/water content index detector 27 adetects presence or absence of water at the irradiation position ofreference beam LS1 and measuring beam LS2 of plant PT based on output(peak information) of comparator/peak hold 25 c in diffuse reflectionlight RV1 of reference beam LS1 and output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV2 of measuringbeam LS2.

In detail, threshold level setter/water content index detector 27 atemporarily stores, for example, output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV1 of referencebeam LS1 in memory 27 b, and next, waits until the output (peakinformation) of comparator/peak hold 25 c in diffuse reflection lightRV2 of measuring beam LS2 is obtained. Threshold level setter/watercontent index detector 27 a obtains output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV2 of measuringbeam LS2, and then calculates a ratio of output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV1 of referencebeam LS1 and output (peak information) of comparator/peak hold 25 c indiffuse reflection light RV2 of measuring beam LS2 in the same line ofplant PT that are contained in the angle of view with reference tomemory 27 b.

For example, at the irradiation position at which there is water, sincea portion of measuring beam LS2 tends to be absorbed, intensity (thatis, amplitude) of diffuse reflection light RV2 is attenuated.Accordingly, it is possible for threshold level setter/water contentindex detector 27 a to detect presence or absence of water at theirradiation position of reference beam LS1 and measuring beam LS2 basedon a calculation result (for example, calculation result of difference(difference ΔV of amplitude) of each intensity of diffuse reflectionlight RV1 and diffuse reflection light RV2 or intensity ratio of diffusereflection light RV1 and diffuse reflection light RV2) of each line ofplant PT which is contained in the angle of view.

Note that, threshold level setter/water content index detector 27 a maydetect presence or absence of water at the irradiation position ofreference beam LS1 and measuring beam LS2 of plant PT (refer to FIG. 5)according to a comparison of the size of rate RT of amplitude differencebetween amplitude VA of diffuse reflection light RV1 of reference beamLS1 and amplitude VB of diffuse reflection light RV2 of measuring beamLS2 (VA−VB) and amplitude VA with predetermined detection thresholdlevel M.

Furthermore, threshold level setter/water content index detector 27 acalculates an intensity rate of diffuse reflection light RV1 and diffusereflection light RV2, that is, reflection intensity rate (also referredto as measurement value) Ln (I905/I1550) and obtains the water contentindex which is equivalent to water content that is contained in the leaffrom the sum total of reflection intensity rate Ln (I905/I1550).Reflection intensity rate Ln (I905/I1550) is calculated, for example, ineach predetermined pixel number (4×4 pixels) in all pixels in the frameimage that is imaged by visible light camera VSC, and is expressed asreflection intensity rate W1 to Wk in each predetermined pixel number.

Memory 27 b is configured using, for example, a random access memory(RAM), and temporarily stores output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV1 of referencebeam LS1.

Detection result filter 27 c filters and extracts information whichrelates to detection result of water from detection camera 1 based onoutput of threshold level setter/water content index detector 27 a.Detection result filter 27 c outputs information which relates to theextraction result to display processor 29. For example, detection resultfilter 27 c outputs information which relates to the extraction resultof water at the irradiation position of reference beam LS1 and measuringbeam LS2 of plant PT to display processor 29.

Display processor 29 uses output of detection result filter 27 c andgenerates detection result image data that indicates the position ofwater at the irradiation position at each distance from detection camera1 as an example of information which relates to water at the irradiationposition. Display processor 29 outputs detection result image data whichincludes information on distance from detection camera 1 to theirradiation position to display controller 37 of visible light cameraVSC.

Next, each part of visible light camera VSC will be described. Imagingoptics 31 is configured using, for example, a lens, ambient light RV0from in the angle of view of detection camera 1 is concentrated, andambient light RV0 forms an image on a predetermined imaging area ofphoto detector 33.

Photo detector 33 is an image sensor which has a peak of spectralsensitivity with respect to wavelength of visible light (for example,0.4 to 0.7 μm). Photo detector 33 converts an optical image that formsan image on the imaging surface to the electrical signal. Output ofphoto detector 33 is input to image signal processor 35 as theelectrical signal. Note that, imaging optics 31 and photo detector 33function as an imaging unit in visible light camera VSC.

Image signal processor 35 uses the electrical signal which is output ofphoto detector 33, and visible light image data is generated which isspecified by a person in recognizable red, green, and blue (RGB),brightness and color difference (YUV), and the like. Thereby, visiblelight image data that is imaged by visible light camera VSC formsvisible light camera image data. Image signal processor 35 outputsvisible light image data to display controller 37.

In a case where display controller 37 uses visible light image data thatis output from image signal processor 35 and detection result image datathat is output from display processor 29, and detects water at anyposition of the visible light image data, display data in which visiblelight image data and detection result image data are composited, ordisplay data which comparatively represents the visible light image dataand detection result image data are generated as examples of informationrelated to water. Display controller 37 (output unit) prompts display bytransmitting display data to data logger DL or communication terminal MTthat are connected via, for example, a network.

Data logger DL transmits display data that is output from displaycontroller 37 to communication terminal MT or one or more externallyconnected device, and prompts display of display, data on a displayscreen of communication terminal MT or one or more externally connecteddevice (for example, monitor 50 within the control room in the officeindicated in FIG. 1).

Communication terminal MT is, for example, a portable communicationterminal which is used by an individual user, receives display data thatis transmitted from display controller 37 via the network, and displaysdisplay data on the display screen of communication terminal MT.

Description of Example of Initial Operation in Invisible Light SensorController

Next, an example of an initial operation in controller 11 of invisiblelight sensor NVSS of detection camera 1 of the present embodiment willbe described with reference to FIG. 4. FIG. 4 is a flow chartillustrating an example of an initial setting operation in controller 11of detection camera 1.

When controller 11 instructs settings of threshold level Sh. ofreflection intensity rate for identifying the shape of the leaf withrespect to threshold level setter/water content index detector 27 a,threshold level setter/water content index detector 27 a calculates andsets threshold level Sh (S1). Details of the process in which thresholdlevel Sh is set will be described in detail. Note that, in a case wherethreshold level Sh is a fixed value, the process of step S1 may beomitted.

In addition, controller 11 sets detection threshold level M of water indetection processor 27 of invisible light sensor NVSS in threshold levelsetter/water content index detector 27 a (S2). It is preferable toappropriately provide detection threshold level M according to aspecific material that is a detection target.

After the process of step S2, controller 11 outputs a control signal forstarting an imaging process to each part of visible light camera VSC(S3-1), and furthermore, outputs to first beam source 13 and second beamsource 15 of invisible light sensor NVSS timing signal for beam scanningTR for starting incidence of reference beam LS1 and measuring beam LS2to first beam source 13 and second beam source 15 (S3-2). Note that,either an execution timing of an operation of step S3-1 or an executiontiming of an operation of step S3-2 may be first, or may besimultaneous.

FIG. 5 is a principle explanatory diagram of detection of water ininvisible light sensor NVSS. For example, threshold level setter/watercontent index detector 27 a may determine that water is detected ifRT>M, and may determine that water is not detected if RT≤M. In thismanner, threshold level setter/water content index detector 27 a is ableto eliminate influence of noise (for example, disturbance light) and isable to detect presence or absence of water with high precision bydetecting presence or absence of water according to a comparative resultof rate RT between amplitude difference (VA−VB) and amplitude VA anddetection threshold level M.

FIG. 6 is a graph illustrating the near infrared spectra of water (H₂O).A horizontal axis of FIG. 6 indicates wavelength (nm), and a verticalaxis of FIG. 6 indicates transmittance (transparency) (%). As shown inFIG. 6, since reference beam LS1 of wavelength 905 nm has transmittancein water (H₂O) that is close to 100%, it is understood that referencebeam LS1 has a characteristic of tending not to be absorbed in water. Inthe same manner, since measuring beam LS2 of wavelength 1550 nm hastransmittance in water (H₂O) that is close to 10%, it is understood thatmeasuring beam LS2 has a characteristic of tending to be absorbed inwater. Therefore, in the present embodiment, the wavelength of referencebeam LS1 which is incident from first beam source 13 is 905 nm, and thewavelength of measuring beam LS2 which is incident from second beamsource 15 is 1550 nm.

FIG. 7A is a diagram which describes a summary of an operation whichmeasures the reflection intensity rate of the entirety of the leaf. Anirradiation range of the near infrared beam is set in a range so as toinclude the entirety of the front surface of the leaf. A lightabsorption amount of the near infrared beam (measuring beam) isreflected in a reflection intensity rate using water in which there isup to a depth of approximately tens of p in a thickness direction of theleaf.

In a case where a projection range of the near infrared beam is reduceddue to the leaf having withered, even in a case where the thickness ofthe leaf increases due to the leaf bending or coiling, in the presentembodiment, a total sum of the reflection intensity rate (hereinafterreferred to as a water content index) in all pixels of the leaf is setas an index of water content. Accordingly, the water content index isrepresented by Σ Ln (I905/I1550), and has correlation with waterpotential.

FIG. 7B is a diagram which describes a summary of an operation whichmeasures the reflection intensity rate in which a spot is in a fixedarea. As described above, even if water content per unit area isobtained by radiating while sequentially scanning the near infrared beamwithin a smaller range than the front surface of the leaf, correlationbetween the water content per unit area and water potential is low.

Description of Detailed Operation Relating to Detection of Water orUndulation of Invisible Light Sensor

Next, a detailed operation procedure which relates to detection of waterin invisible light sensor. NVSS of detection camera 1 will be describedwith reference to FIG. 8. FIG. 8 is a flow chart illustrating a detailedoperation procedure which relates to detection of water that iscontained in leaf PT3 of plant PT in invisible light sensor NVSS. As apremise of description of the flow chart illustrated in FIG. 8, timingcontroller 11.a outputs timing signal for beam scanning TR to first beamsource 13 and second beam source 15, and reference beam LS1 andmeasuring beam LS2 from detection camera 1 is radiated toward leaf PT3of plant PT.

In FIG. 8, controller 11 determines whether or not beam output signal RFin incidence period of an odd number of times is output from timingcontroller 11 a (S12). In a case where controller 11 determines thatbeam output signal RF in incidence period of an odd number of times isoutput from timing controller 11 a(S12, YES), first beam source 13incidents reference beam LS1 according to beam output signal RF fromtiming controller 11 a(S13). Beam scanner 17 one-dimensionally scansreference beam LS1 of one line or more in an X direction of plant PTwhich is contained in the angle of view of detection camera 1 (S15). Atthe irradiation position on each line in the X direction on which thereference beam LS1 is radiated, diffuse reflection light RV1 that isgenerated by reference beam LS1 being diffused and reflected is receivedby photo detector 23 via imaging optics 21 (S16).

In signal processor 25, output (electrical signal) in photo detector 23of diffuse reflection light RV1 is converted to the voltage signal, andthe level of the electrical signal is amplified up to a processablelevel in comparator/peak hold 25 c (S17). Comparator/peak hold 25 cbinarizes the output signal of amplifier 25 b and outputs to thresholdlevel setter/water content index detector 27 a according to acomparative result of the output signal of amplifier 25 b and thepredetermined threshold level. Comparator/peak hold 25 c outputs peakinformation of output signal of amplifier 25 b to threshold levelsetter/water content index detector 27 a.

Threshold level setter/water content index detector 27 a temporarilystores output (peak information) of comparator/peak hold 25 c withrespect to diffuse reflection light RV1 of reference beam. LS1 in memory27 b (S18-2). In addition, threshold level setter/water content indexdetector 27 a reads from memory 27 b output of comparator/peak hold 25 cwith respect to the same line in diffuse reflection light RV1 or diffusereflection light RV2 with respect to reference beam LS1 or measuringbeam LS2 in a previous frame (incidence period) that is stored in memory27 b (S18-3).

Threshold level setter/water content index detector 27 a detectspresence or absence of water on the same line based on output (peakinformation) of comparator/peak hold 25 c in diffuse reflection lightRV1 of reference beam LS1 and output (peak information) ofcomparator/peak hold 25 c in diffuse reflection light RV2 of measuringbeam LS2 on the same line and predetermined detection threshold level M(S18-4).

Threshold level setter/water content index detector 27 a calculates thewater content index which is total sum Σ Ln (I905/I1550) of thereflection intensity rate (S18-5). Details of calculation of the watercontent index will be described in detail.

Display processor 29 uses output of detection result filter 27 c andgenerates detection result image data that indicates the detectionposition of water. Display controller 37 outputs detection result imagedata that is generated by display processor 29 and visible light cameraimage data of a visible light image that is imaged by visible lightcamera VSC (S19). Each operation of steps S15, S16, S17, S18-2 to S18-5,and S19 is executed in each line within the detection area of one frame(incidence period).

That is, when each operation of steps S15, S16, S17, S18-2 to S18-5, andS19 is complete with respect to one line in the X direction, eachoperation of steps S15, S16, S17, S18-2 to S18-5, and S19 is performedwith respect to a subsequent line in the X direction (S20, NO),hereinafter until each operation of steps S15, S16, S17, S18-2 to S18-5,and S19 is complete in one frame, each operation of steps S15, S16, S17,S18-2 to S18-5, and S19 is repeated with respect to scanning in a Ydirection indicated in enlarged diagram EPG in FIGS. 7A and 7B.

Meanwhile, in a case where execution of each operation of steps S15,S16, S17, S18-2 to S18-5, and S19 is complete with respect to all linesin one frame (S20, YES), and in a case where scanning of incident lightis continued (S21, YES), an operation of invisible light sensor NVSSreturns to step S12. Meanwhile, in a case where scanning of referencebeam LS1 and measuring beam LS2 is not continued (S21, NO), theoperation of invisible light sensor NVSS is complete.

FIG. 9 is a flow chart illustrating a calculation procedure of a watercontent index in step S18-5. Threshold level setter/water content indexdetector 27 a calculates reflection intensity rate Ln (I905/I1550) inall pixels from the frame image (S31). Here, a measurement value ofreflection intensity rate Ln (I905/I1550) of each pixel is representedby reflection intensity rates W1 to Wk. For example, in a case where theimage of the near infrared beam is configured from 76,800 (=320×240)pixels, a suffix k of Wk is a variable which represents 1 to 76,800.

Threshold level setter/water content index detector 27 a determineswhether or not the reflection intensity rate Wk of each pixel is largerthan threshold level Sh for identifying leaf PT3 (S32). An initial valueof threshold level Sh is registered in advance in threshold levelsetter/water content index detector 27 a as an empirical value. Theempirical value is determined according to a specification of the watercontent evaluation apparatus (intensity of the irradiation laser beam,sensitivity of a light receiving element, and the like), water content(about 90%) of the leaf that is the measurement target, thickness of theleaf (for example, 200 μm), inside/outside (or “indoor/outdoor”), andthe like. In particular, in a case of outside, there is change accordingto how sunlight hits or manner of growth of foliage, and the variable ischanged each time.

For example, as the empirical value, in the case of an imaging distanceof 1 m, threshold level Sh during imaging inside is set to approximately0.3. Threshold level Sh during imaging outside is set to approximately0.9. In addition, in the case of an imaging distance of 3 m, thresholdlevel Sh during imaging inside is set to approximately 0.05. It ispreferable to change threshold level Sh in a case where threshold levelSh is set as the initial value, it is determined whether or not thethreshold level is optimal in comparison to the actual shape of theleaf, and the threshold level is not optimal. In addition, as will bedescribed later, a calculation process of threshold level Sh isperformed, and it is possible to register calculated threshold level Shas the initial value.

In step S32, in a case where reflection intensity rate Wk is less thanthreshold level Sh, the pixel is a pixel that represents a backgroundother than the leaf, and display processor 29 generates monochromaticdisplay data for displaying pixels monochromatically (S36).

Meanwhile, in step S32, in a case where reflection intensity rate Wk isthreshold level Sh or more (threshold level or more), display processor29 displays pixels in a tone color corresponding to reflection intensityrate Ln (I905/I1550) (S33). Here, it is possible to display the tonecolor corresponding to reflection intensity rate Ln (I905/I1550) at ntone. n is an arbitrary positive number. FIG. 10 is a table illustratinga tone color corresponding to the reflection intensity rate. Reflectionintensity rate Ln (I905/I1550) and an intensity ratio (reflection lightof 905 nm/reflection light of 1550 nm) are classified in each gradationcolor in table Tb.

In detail, in a case where reflection intensity rate Ln (I905/I1550) isless than 0.3, that is, in a case of being threshold level Sh of theleaf or less, the pixel is displayed using, for example, white(monochrome). Meanwhile, in a case where reflection intensity rate Ln(I905/I1550) is 0.3 to less than 0.4, the pixel is displayed using, forexample, dark green. In the same manner, in a case of being 0.4 to lessthan 0.5, the pixel is displayed using green. In a case of being 0.5 toless than 0.55, the pixel is displayed using yellow. In a case of being0.55 to less than 0.6, the pixel is displayed using orange. In a case ofbeing 0.6 to less than 0.75, the pixel is displayed using red. In a caseof being 0.75 or more, the pixel is displayed using purple. In thismanner, the color of the pixel that belongs to the leaf is set in any ofsix tones.

Note that, in a case where a pixel space which the leaf occupies is notappropriate in comparison to the actual shape of the leaf, the user mayset threshold level Sh up or down in each predetermined increment (forexample, 0.01). Alternatively, the user may set appropriate thresholdlevel Sh by activating a process (refer to FIG. 13) in which thresholdlevel Sh described later is automatically set.

Threshold level setter/water content index detector 27 a specifies anarea of the pixel space which the leaf occupies (S34). FIG. 11 is atable illustrating the reflection intensity rate in a portion of a frameimage which includes a pixel space that the leaf occupies. As a portionof the frame image, reflection intensity rate Ln (I905/I1550) of 21pixels×9 pixels is indicated in the table. The pixels where thebackground is green (dot display) is equivalent to pixels of the leaf.As described above, pixels of the leaf are pixels in which reflectionintensity rate Ln (I905/I1550) exceeds threshold level. Sh (here, 0.3).In addition, an area ARE of a rectangle (A×B) is specified such that thepixels of the leaf are enclosed. The area. ARE is used as a value whichdetermines the size of the leaf. Note that, the size of the leaf mayrepresent the pixel number which exceeds threshold level Sh.

Threshold level setter/water content index detector 27 a (water contentcalculation unit) calculates water content index Σ Ln (I905111550) thatis a sum total of reflection intensity rate Ln (I905/I1550) where ameasurement value (reflection intensity rate Ln (I905/I1550)) is largerthan threshold level Sh in area ARE (S35). Water content which iscontained in the entirety of the leaf is understood by obtaining watercontent index Σ Ln (I905/I1550).

Furthermore, in step S35, it is possible for threshold levelsetter/water content index detector 27 a to calculate the number ofpixels in which the measurement value (reflection intensity rate Ln(I905/I1550)) is larger than threshold level Sh in area ARE, andcalculate an average value by dividing total sum Σ Ln (I905/I1550) ofthe reflection intensity rate by the number of calculated pixels. Theaverage value is a value in which the total sum of the reflectionintensity rate is divided by the area of the leaf where the externalform of the leaf is determined by threshold level Sh, and a value inwhich the total sum of the reflection intensity rate in a spot isdivided by a fixed area of the spot and a value in which the total sumof the reflection intensity rate is divided by the area that is enclosedby the external form of the leaf in the visible image are different.After this, the calculation operation of the water content index ends.

In this manner, in the present embodiment, the reflection intensity rateof each irradiation position is not obtained, the reflection intensityrate of each pixel in the frame image is obtained, and it is possible tocorrectly calculate the water content index from the total sum ofreflection intensity rate of each pixel. Accordingly, it is possible toaccurately determine status of the leaf, that is, the plant.

Here, as described above, threshold level Sh of the leaf is set to asubsequent value as the initial value. In a case where detection camera1 is installed inside and leaf PT3 is imaged inside, and in a case whereimaging distance is empirically 1 m, threshold level Sh is set toapproximately 0.3. In the case of an imaging distance of 3 m, thresholdlevel. Sh is set to approximately 0.05. Meanwhile, in a case of imagingoutside, since a condition of sunlight varies, threshold level Sh isempirically set to approximately 0.9. FIGS. 12A to 12C are diagramsillustrating an occupancy range of the leaf. FIG. 12A is a frame imagethat images stalks and leaves of a tomato. A distance between leaves isapproximately 1 cm. FIG. 12B illustrates the occupancy space of the leafwhich is obtained in a case where the imaging distance is set to 3 m andthreshold level Sh is set to 0.05 with respect to the visible lightimage in FIG. 12A. In this case, it is understood that the leavesoverlap in portions and threshold level Sh (=0.05) is a value that isinappropriately set. FIG. 12C illustrates the occupancy space of theleaf which is obtained in a case where the imaging distance is set to 1m and threshold level Sh is set to 0.3 with respect to the visible lightimage in FIG. 12A. In this case, the outer form of the leaf does notoverlap with another leaf, in addition, the occupancy space of the leafis the same as the size of the outer form of the leaf of the visiblelight image. In this case, it is understood that threshold level Sh(=0.3) is a value that is correctly set.

In addition, threshold level Sh of the leaf may not be registered beforethe subsequent process is performed and the calculation process of thewater content index indicated in FIG. 9 is executed. FIG. 13 is a flowchart illustrating a threshold level setting procedure.

Threshold level setter/water content index detector 27 a obtains anoccupancy rate that is determined as the leaf KG pixel number/all pixelnumbers), i.e. a pixel occupancy of green (G) that is determined as thecolor of the leaf with respect to the frame image (for example, refer toFIG. 12A) that is imaged by visible light camera VSC (S41).

Threshold level setter/water content index detector 27 a obtains thewater index corresponding to the occupancy rate of the leaf based onfrequency distribution data of the water content index (S42). FIG. 14 isa graph illustrating the frequency distribution of the reflectionintensity rate in all pixels. Frequency distribution data is registeredin threshold level setter/water content index detector 27 a. When usingthe frequency distribution data, in a case where, for example, theoccupancy rate of the leaf is 52%, the water content index isapproximately 0.3.

Threshold level setter/water content index detector 27 a sets the watercontent index that is obtained in step S42 to threshold level Sh (S43).After this, threshold level setter/water content index detector 27 aends the present process.

In this manner, it is possible to correctly determine the outer form ofthe leaf by obtaining an occupancy pixel number of green (specifiedcolor) of the leaf and threshold level Sh corresponding to cumulativefrequency of Ln (I905/I1550) that is the measurement value which is thesame pixel number by utilizing the visible light image that is imaged byvisible light camera VSC, that is, by modifying the threshold level ofthe water content of each pixel that is contained in the leaf.Accordingly, it is possible to accurately calculate the average value ofthe pixel unit by correctly determining the outer form of the leaf. Incontrast to this, in a case where the fixed area of the spot or theouter form of the visible light image is used, when the outer form ofthe leaf is not correctly captured, a large error is generated in theaverage value of the pixel unit.

In FIGS. 4 to 14, water content of the leaf is calculated based on thepixel with a part that is determined to be the outer form of the leafbeing set as the outer form of the leaf and has a higher water contentthan the outer form of the leaf by setting the one threshold level ofwater content. However, the water content of the leaf may be calculatedusing the threshold level for determining the outer form of the leaf anda plurality of threshold levels compiled from other threshold levels.For example, another threshold level may be set in order to exclude thepixel which is equivalent to a leaf vein, and in particular, a main veinfrom the calculation target of the water content of all leaves. The leafvein is a transportation route for water or nourishment. Therefore, evenif water content of all leaves reduces, the water content of, forexample, the leaf vein, and in particular, the main vein tends not torelatively reduce more than another part. Furthermore, since anincidence direction of sunlight with respect to the leaf changes withtime, the threshold level may be set to a different value according tothe measurement time.

FIG. 15A is a diagram illustrating the leaf that is fixed in variouspostures during measurement. In water measurement of the leaf, whitereference substrate bd is prepared as a plate material that has a flatsurface, and leaf PT3 is affixed using double-sided tape such that therear surface of leaf PT3 overlaps with the surface of the platematerial. In first water measurement, the plate material is set so as tobe a vertical plane with respect to an optical axis of detection camera1. In second water measurement, the plate material is set so as to beinclined at a tilt angle of 45° with respect to the optical axis ofdetection camera 1. In third water measurement, the plate material isset so as to be inclined at a pan angle of 45° with respect to theoptical axis of detection camera 1.

FIG. 15B is a diagram illustrating an image which represents thereflection intensity rate of the leaf. In first water measurement, thearea in which the reflection intensity rate exceeds threshold level Shis close to the outer form of the leaf viewed from a front surface. Inaddition, it is understood that the reflection intensity rate in thecenter of the leaf maximally increases from the inside of the leaf andthe reflection intensity rate gradually lowers. In second watermeasurement, the area in which the reflection intensity rate exceedsthreshold level Sh is close to the outer form of the leaf with the leafviewed inclined in the tilt direction. In addition, the reflectionintensity rate is high across a wide range inside the leaf. Thethickness of the leaf increases in the optical axis direction due to theleaf tilting with respect to the optical axis, and as apparent, isconsidered to be due to water content of the leaf becoming great. Inthird water measurement, the area in which the reflection intensity rateexceeds threshold level Sh is close to the outer form of the leaf withthe leaf viewed inclined in the pan direction. In addition, thereflection intensity rate is high across a wide range inside the leaf.In the same manner as the case of the second water measurement, thethickness of the leaf increases in the optical axis direction due to theleaf tilting with respect to the optical axis, and as apparent, isconsidered to be due to water content of the leaf becoming great.

FIG. 16 is a graph illustrating the reflection intensity rate withrespect to an average content. According to the graph, in the total sum(water content index) of the reflection intensity rates that arerespectively obtained in first, second, and third water contentmeasurement, the larger an average water content of the leaf, the largerthe value becomes, and there is a high correlation with respect to theaverage water content. In first water content measurement, square (R2)of correlation coefficient is 0.9943. In second water contentmeasurement, square (R2) of correlation coefficient is 0.9973. In thirdwater content measurement, square (R2) of correlation coefficient is0.963. In this manner, in the case of any water content measurement, thewater content index has high correlation with respect to the averagewater content.

Next, a tomato seedling is used, and a wilting process and root waterabsorption (revival) process are indicated after irrigation stops(suspension of water supply). FIG. 17A is a graph illustrating a wiltingprocess of the plant. The vertical axis indicates the water contentindex of one leaf (=Σ Ln (I905/I1550), and the horizontal axis indicatesan elapsed time from the start of suspension of water supply. Curve Lf11indicates the water content index of the leaf with reference to a casewhere irrigation is performed two times, morning and evening, in oneday. Curve 1112 indicates a case in which irrigation is not performedagain after a wilting point is reached in a case where the irrigation isstopped (water supply is suspended). In addition, in FIG. 17A, invarious marks of curve Lf11 and curve Lf12, the start of the marksindicate around 9 am and the end of the marks indicate around 5 μm, anda mass of the number of the various marks indicate a range from around 9am until around 5 μm in one day.

When the average water content of the leaf gradually reduces from 86%while exceeding the time of the water supply suspension time and watersupply suspension time exceeds 330 hours, the wilting point of watercontent 50% or less is reached. In the leaf in a case where water supplyis not suspended, and irrigation is performed every day regularly twice,in the morning and evening, as indicated in curve Lf11, the averagewater content of the leaf is maintained at substantially the same value(water content index: value 110) as the measurement initialization.Meanwhile, in the leaf in which water supply continues to be suspended,as apparent, when average water content of the leaf continues to lowerafter the wilting point at which stalks and leaves wilt and the watersupply suspension time is 350 hours, the water content index is loweredto a value 20.

FIG. 17B is a graph illustrating a revival process. After the watercontent index of the leaf lowers to the value 20, when irrigation isperformed again, the average water content of the leaf gradually raisesalong with elapsing of the time after irrigation is performed again.When the elapsed time reaches 280 minutes, the average water content ofthe leaf to which water supply is suspended reaches a value (watercontent index: 100) close to the average water content of the leaf priorto the water supply being suspended.

FIG. 18 illustrates a process in which water content of the leaf thatapproaches wilting gradually increases using actual measurement data(diagram in which a reflection intensity rate table of a frame imagedisplays tone) used when the graph of the revival process in FIG. 17B isplotted. In a case where the elapsed time from performing irrigationagain is 0 minutes, when the area of the leaf in which reflectionintensity rate Ln (I905/I1550) exceeds threshold level Sh is small and60 minutes elapse, there is a slight increase, and when 300 minuteselapse, there is a further increase. Then, it is understood that thewater content of the leaf is revived until an equal level as whenirrigation is regularly performed in the morning and evening where thewater supply is not suspended (left side leaves of each frame images inthe diagram equivalent to curve Lf11 in FIG. 17B).

In this manner, it is possible to visually grasp the wilting process andthe root water absorption (revival) process by measuring the watercontent which is contained in the leaf.

Comparative Example

FIG. 19 is a diagram which describes a measurement method of acomparative example. Macrophyll leaf PT3 that is sealed and packed invinyl bag fk is taken out and fixed to white board wb such that leaf PT3does not move. White board wb that is firmly fixed to leaf PT3 is placedon weight scale gm, and the weight is measured. At this time, since theweight of white board wb is measured in advance, and is adjusted by 0points, the weight of the leaf is displayed on a meter of weight scalegm. Change of weight due to transpiration of the leaf is measured whilethe time elapses. After all measurement ends, the leaf completely driesand the weight is obtained. The average water content of the leaf duringmeasurement is obtained by deducting the weight of the leaf duringdrying from the weight of the leaf during measurement. FIG. 20A is agraph illustrating a time change of weight of the leaf due totranspiration, that is, time change of average water content of theleaf. The average water content substantially lowers while the timeelapses.

In addition, white board wb to which leaf PT3 is fixed is placed in astanding state. In this state, visible light camera VSC1 images theleaf. Furthermore, invisible light camera NVSS1 respectively radiatesthe near infrared beam which has a wavelength of 905 nm and a wavelengthof 1550 nm with respect to 12 locations on the leaf, and reflectionintensity rate Ln (I905/I1550) is measured. The 12 locations on the leafare areas that are set across the entire leaf, and have a size of 4×4pixels. FIG. 20B is a graph illustrating time change of reflectionintensity rate Ln (I905/I1550) that is measured at 12 locations on theleaf.

FIG. 20C is a graph which is obtained based on measurement data of FIGS.20A and 20B, and illustrating a correspondence relationship ofreflection intensity rate Ln (I905/I1550) and the average water content.At any of the 12 locations on the leaf, there is a proportionalrelationship of reflection intensity rate Ln (I905/I1550) and theaverage water content. Accordingly, in a case where the leaf is firmlyfixed so as not to move, the average water content on the leaf isunderstood by measuring reflection intensity rate Ln (I905/I1550).

In this manner, in the water content evaluation apparatus in the firstembodiment, first beam source 13 of detection camera 1 radiates the nearinfrared beam (reference beam) of first wavelength (905 nm) that has acharacteristic of tending not to be absorbed in water toward leaf PT3 ofplant PT by optical scanning. Second beam source 15 of detection camera1 radiates the near infrared beam (measuring beam) of second wavelength(1550 nm) that has a characteristic of tending to be absorbed in watertoward leaf PT3 of plant PT by optical scanning. Threshold levelsetter/water content index detector 27 a calculates the water contentindex of one leaf that is total sum Σ Ln (I905/I1550) of reflectionintensity rate based on a reflection light of 905 nm on all irradiationpositions of leaf PT3 and a reflection light of 1550 nm on allirradiation positions of leaf PT3. Therefore, it is possible toaccurately measure water content which is contained in the plant that isthe index of status of the plant.

In addition, threshold level setter/water content index detector 27 aholds threshold level Sh which indicates the water content andidentifies the shape of one plant, and adds water content in at leastone irradiation position that is threshold level Sh or more. Thereby, itis possible to appropriately calculate water content of the plant usingthreshold level Sh.

In addition, visible light camera VSC acquires the visible light imageof the plant, and threshold level setter/water content index detector 27a calculates threshold level Sh using the visible light image of theacquired image. Thereby, it is possible to set threshold level Sh whichis able to correctly identify the shape of the plant.

In addition, display controller 37 outputs at least one invisible lightimage out of leaf, seed, stalk, and flower of the plant. Thereby, it ispossible to confirm whether or not the shape of the plant is correctaccording to the output invisible light image.

In addition, threshold level setter/water content index detector 27 acalculates water content at each irradiation position, and calculatesthe water content at all irradiation positions of the plant by addingthe calculated water content. Display controller 37 displays theinvisible light image in steps to be identifiable according to the watercontent which is calculated at each irradiation position. Thereby, it ispossible to visually recognize the distribution of water content whichis contained in the plant other than the water content of the entireplant.

In addition, each irradiation position corresponds to a pixel of apredetermined number in the invisible light image. Thereby, it ispossible to associate the position of the plant and the position of theinvisible light image.

Details and Problems of Second Embodiment

In a case where the front surface of the leaf of the plant is irradiatedwith two types of near infrared beam and water from the reflectionintensity rate is obtained, there is the following problem. Whenmeasuring by radiating the near infrared beam, the near infrared beam(for example, pulsed light) is radiated on the leaf that is themeasurement target, and the part of the light which is diffused andreflected in all directions on the front surface of the leaf is receivedand measured in a detection unit for the near infrared light by slightlyshifting the irradiation timing (for example, by shifting a μ SECorder). In addition, the light radiated here is the laser beam,therefore the wavelength width is narrow by only a wavelength at theunit wavelengths of 905 nm and 1550 nm. Furthermore, the detection unitfor the near infrared light is not for the unit wavelength (a filterthrough which only 905 nm and 1550 nm pass or the like which is notattached), and is a photoelectric converter (photosensor) whichelectrically changes light of a near infrared light region of a widerange.

Here, there is a problem when receiving light in the detection unit ofthe near infrared light, but there is sunlight that is external light.Sunlight has a wide wavelength area different from the laser beam, andhas any wavelength in the near infrared light area. Sunlight is dividedinto “directly reflected light” in which a part of sunlight is directlyreflected at the leaf that is the measurement target and “multiplescattering light” which is subjected to multiple scattering betweenperipheral leaves as indicated in FIG. 22A. Then, such that the timingof both during radiation of the near infrared beam of 905 nm and duringradiation of the near infrared beam of 1550 nm are the same, thereflection intensity rate of 905 nm/1550 nm is significantly raised bythe near field spectra indicated in FIG. 6. So, when there is asignificant rise in the background, it is difficult to distinguishindividual measurement target leaves and peripheral leaves.

In addition, the leaves of a seedling in a field grow in abundance andbecome foliage. In the foliage, a plurality of leaves overlap isrespective orientations, and for example, when wind blows, the leavesrelatively move. For example, as shown in FIG. 21A, in a case where thenear infrared beam is radiated toward leaf PT3 t that is the measurementtarget, the radiated near infrared beam is absorbed and scattered byleaf PT3 o that is on the periphery of leaf PTt that is the measurementtarget. As indicated by arrow b1, other than, for example, the radiatednear infrared beam being absorbed by leaf PT3 t that is the measurementtarget, as indicated by arrow b2, leaf PT3 o on the left side is alsoradiated and a portion is absorbed. Leaf PT3 o on the left side isradiated, and the near infrared beam that is scattered by leaf PT3 o onthe left side is diffused on leaf PT3 t that is the measurement target.In addition, as indicated by arrow b3, multiple scattering also occursin which leaf PT3 r 1 on the right side is radiated, and diffused lightthat is scattered by leaf PT3 r 1 on the right side is diffused to otherleaf PT3 r 2 and is diffused on leaf PT3 t that is the measurementtarget. Water content of target leaf PT3 t contains the water contentabsorbed by the peripheral leaf; and is measured to be greater than inreality. In addition, as shown in FIG. 21B, a plurality of leavesoverlap or are separated, and the area of the leaf is changed.

Accordingly, even in measurement of presence or absence of watercontent, individual leaves on the periphery of the target leaf aredifficult to distinguish.

Therefore, it is possible to eliminate influence due to scattered light(for example, light scattered externally such as sunlight) from theperipheral leaf and accurately measure water content of the leaf that isthe measurement target even within the foliage in which multiple leavesgrow in abundance.

Second Embodiment

A configuration of a water content evaluation apparatus of the secondembodiment is substantially the same configuration as the firstembodiment. The same reference numerals are used for the configuringelements which are the same as in the first embodiment, and thereforethe description is omitted.

The leaf of the plant that is the measurement target is a leaf that isrepresentative of the plant in for example, a plastic greenhouse,temperature, humidity, illumination, and ventilation are set in alocation with different CO₂ concentrations.

FIG. 21A is a diagram which describes a summary of an operation of thewater content evaluation apparatus in the second embodiment. FIG. 21B isa diagram illustrating overlapping of leaves. In the water contentevaluation apparatus, a background material is disposed so as to cover aback surface (rear side) of the leaf that is the measurement target.

As the material of the background material, a material that does notcontain water and that does not deform due to pesticide, sprinkling, orCO₂ spraying is given such as plastic, coated paper, sheets such asaluminum foil (plate), a plate, or a block. In addition, it is desirablethat the size of the background material has a large surface such thatthe leaf that is the measurement target is covered and is a size so asnot to interfere with photosynthesis of another leaf within two timesthe projection area of the leaf that is the measurement target. Inaddition, it is preferable that the thickness of the background materialis a thickness of 50 μm to 1 mm self-supporting without curling, and inparticular, 50 to 200 μm. In addition, in a case of being supported bythe stalk of the leaf, it is preferable that the weight of thebackground material is a weight to a degree that the leaf does not wilt.In addition, it is preferable that the color of the background materialis white or silver with high reflectance of visible light and the nearinfrared beam.

In the present embodiment, as the background material, a case of using awhite reference substrate is indicated. Note that, a white plasticplate, an aluminum plate, a standard white plate, white paper, and thelike are given as the white reference substrate.

FIG. 22A is a graph illustrating reflection light intensity with respectto wavelength of the near infrared beam when near infrared beam isradiated toward the leaf outdoors. The vertical axis indicates intensityof the near infrared light which is detected by invisible light sensorNVSS, and the horizontal axis indicates wavelength of a near infraredarea. Intensity of light that is scattered by the peripheral leaf otherthan intensity of light according to sunlight is included in intensityof the near infrared light which is detected by invisible light sensorNVSS. That is, a rise of the background due to multiple scattering ofsunlight being carried out on the peripheral leaf is included in theintensity of the detected near infrared light. In addition, intensity oflight detected by invisible light sensor NVSS is small due to the nearinfrared beam which has a wavelength of 1550 nm being absorbed by theperipheral leaf. Accordingly, the value of reflection intensity rate Ln(I905/I1550) is large. Therefore, in a case where water content of theleaf outside is measured, it is necessary to set the value of thresholdlevel Sh that is compared to reflection intensity rate Ln (I905/I1550)to be large.

FIG. 22B is a graph illustrating reflection light intensity with respectto wavelength of the near infrared beam when near infrared beam isradiated toward the leaf on which white reference substrate bd isinstalled indoors and outdoors. The vertical axis indicates intensity ofthe near infrared beam which is detected by invisible light sensor NVSS,and the horizontal axis indicates the wavelength of a near infraredarea. Multiple scattering from peripheral leaf PT3 o does not occur dueto white reference substrate bd being disposed to cover the back surface(rear side) of leaf PT3 t that is the measurement target. Accordingly, alowering of intensity of the near infrared beam which has a wavelengthof 1550 nm does not occur. In addition, in the case of inside, a rise ofthe background does not occur. Note that, in a case of measuringoutside, threshold level Sh is set to approximately 0.5. In addition, ina case of measuring inside, threshold level Sh is set to approximately0.3.

In a case where white reference substrate bd is disposed on the backsurface of leaf PT3 t that is the measurement target, the leaf may bedisposed without being fixed, and leaf PT3 t may be attachably fixed towhite reference substrate bd. Here, a case where leaf PT3 t is attachedto white reference substrate bd is illustrated.

FIG. 23 is a diagram which describes attachment of leaf PT3 t on whitereference substrate bd. White reference substrate bd is a white plasticplate which has a vertical rectangular shape. Aperture bd1 that ishollowed out in a rectangular shape is formed in the center of whitereference substrate bd. In addition, round hole bd2 is formed in anupper portion of white reference substrate bd. Slit bd21 which reachesup to an upper end surface is formed on hole bd2. In addition, threeslits bd3, bd4, and bd5 are respectively formed on the lower side andboth sides of aperture bd1 that is formed on white reference substratebd.

In a case where leaf PT3 t is attached to white reference substrate bd,a tip end of leaf PT3 t is inserted into one of three slits bd3, a voidis generated by shifting horizontal white reference substrate bd in alongitudinal direction centered on slit bd21, stalk PT2 of the leafpasses inside, and stalk PT2 is fixed to hole bd2.

FIG. 24 is a diagram illustrating various installation methods of whitereference substrate bd that is installed so as to cover the rear surfaceof leaf PT3 t that is a measurement target. In the diagram, in plant PTon the left side, white reference substrate bd is attached to the tipend of rod p1 that stands on base BB, and is installed as a noticeboard. In addition, in center plant PT, white reference substrate bd isheld in a state of hanging down from attractant line rp1 due toattractant string rp2. In addition, in plant PT on the right side in thediagram, white reference substrate bd is held by stalk PT2 that passesthrough round hole bd2.

FIG. 25A is a photo illustrating leaf PT3 t that is the measurementtarget of water content outside. Here, white reference substrate bd isinstalled as the notice board. In addition, plurality of leaves PT3protrude to stalk PT2 which protrudes from hole bd2 of white referencesubstrate bd, and one leaf (leaf enclosed by frame e) PT3 t therein isset as the measurement target. In addition, as a comparative example,leaf (leaf enclosed by frame fin the diagram) PT3 h on which the whitereference substrate is not disposed on the back surface is set as themeasurement target.

FIG. 25B is a diagram illustrating reflection intensity rate Ln(I905/I1550) of leaf PT3 t. FIG. 25C is a diagram illustratingreflection intensity rate Ln (I905/I1550) of leaf PT3 h. On leaf PT3 h,since white reference substrate bd is not present, reflection intensityrate of leaf PT3 h is increased due to scattered light of the leaf inthe periphery due to sunlight. FIG. 26A is a table illustrating thereflection intensity rate in a portion of a frame image which includes apixel space that leaf PT3 t occupies which is covered by the backsurface on white reference substrate bd. Area ARE1 in which reflectionintensity rate Ln (I905/I1550) of leaf PT3 t exceeds threshold level Sh(=0.3) is close to the shape of leaf PT3 t, and it is considered thatthe outer form of the leaf is expressed. Meanwhile, FIG. 26B is a tableillustrating the reflection intensity rate in a portion of the frameimage which includes the pixel space that leaf PT3 h occupies which isnot covered by the back surface on white reference substrate bd.Reflection intensity rate Ln (I905/I1550) of leaf PT3 h is large due toscattered light from peripheral leaf PT3 o, and it is considered that anerror is included. In addition, area ARE2 in which reflection intensityrate Ln (I905/I1550) of leaf PT3 h exceeds threshold level Sh (=0.9) isnot similar to the outer form of leaf PT3 h that is slightly verticallyshaped, and it is considered that the outer form of leaf PT3 h is notexpressed.

FIG. 27 is a photo illustrating the leaf that is the measurement targetof half of the water content outside. In a first half measurement, leafPT3 t that is a high location is set as the measurement target enclosedby frame g1, and white reference substrate bd is disposed on the backside. In a second half measurement, leaf PT3 i 1 that is a low locationis set as the measurement target enclosed by frame g2, and whitereference substrate bd is disposed on the back side. In a third halfmeasurement, plurality of leaves PT3 i 2 are set as measurement targetsenclosed by frame g3, and nothing is disposed on the back side. In afourth half measurement, foliage PT3 i 3 in which multiple leaves growin abundance is set as the measurement target enclosed by large frameg4, and nothing is disposed on the back side.

FIG. 28A is a graph illustrating the time change of the water contentindex of leaf PT3 t in the first half measurement and leaf PT3 i 1 inthe second half measurement. The vertical axis is the water contentindex which is expressed by reflection intensity rate Ln (I905/I1550),and the horizontal axis is time (unit: mins). In addition, presence orabsence of a half is determined according to whether or not the watercontent index is halved to ½ from a liquid fertilizer that is suppliedto the plant being cut off (refer to broken line h1). The same alsoapplies to FIGS. 28B and 28C.

When white reference substrate bd is disposed on the back side, eitherleaf PT3 t at the high location and leaf PT3 i 1 at the low location,and approximately 1200 minutes elapse from supply of the liquidfertilizer being cut off, half of the water content index is confirmed.

FIG. 28B is a graph illustrating the time change of the water contentindex of leaf PT3 i 2 in the third half measurement. In leaf PT3 i 2 inwhich white reference substrate bd is not disposed on the back, althougha background of reflection intensity rate Ln (I905/I1550) due todiffused reflection from the peripheral leaf is slightly large incomparison to leaf PT3 t and PT3 i 1, when approximately 1200 minuteselapse from supply of the liquid fertilizer being cut off, half of thewater content index is confirmed.

FIG. 28C is a graph illustrating the time change of the water contentindex of foliage PT3 i 3 in the fourth half measurement. In leaf PT3 i 3in which white reference substrate bd is not disposed on the backsurface, although the background of reflection intensity rate Ln(I905/I1550) due to diffused reflection (light scattered externally)from the peripheral leaf is significantly large, when approximately 1200minutes elapse from supply of the liquid fertilizer being cut off, halfof the water content index is not able to be confirmed. Accordingly, inthe foliage, even if overlapping leaves (refer to FIG. 21B) appear ordisappear, and reflection intensity rate Ln (I905/I1550) is measured, itis understood that the error is large.

In this manner, in the water content evaluation apparatus in the secondembodiment, when the water content of the leaf (or the part of theplant) is evaluated, white reference substrate bd (background material)is disposed so as to cover the back surface of leaf PT3 of plant PT.First beam source 13 radiates near infrared beam (reference beam) ofwavelength 905 nm that has a characteristic of tending not to beabsorbed in water toward leaf PT3 by optical scanning. Second beamsource 15 radiates near infrared beam (measuring beam) of wavelength1550 nm that has a characteristic of tending to be absorbed in watertoward leaf PT3 by optical scanning. Threshold level setter/watercontent index detector 27 a calculates the water content index of oneleaf that is total sum Σ Ln (I905/I1550) of the reflection intensityrate at all irradiation positions of leaf PT3 based on the reflectionlight of the reference beam that is reflected on all irradiationpositions of leaf PT3 and the reflection light of the measuring beamthat is reflected on all irradiation positions of leaf. PT3. Thereby, itis possible to eliminate influence due to scattered light (lightscattered externally) from the peripheral leaf and accurately measurethe water content of the leaf that is the measurement target by removinginfluence of overlap and the like even within the foliage in whichmultiple leaves grow in abundance.

In addition, white reference substrate bd is the notice board standingin front of leaf PT3 of the plant. Thereby, it is possible to disposewhite reference substrate bd in a state of being installed independentlyfrom the plant, and it is possible to firmly fix. Accordingly, even tothe extent of external force or disbudding of wind, rain, and the like,and artificial external force during leaf work being applied, it ispossible to maintain a posture of white reference substrate bd.

In addition, white reference substrate bd hangs down from above theplant using attractant string rp2. Thereby, it is possible to disposewhite reference substrate bd in a state in which leaf PT3 of the plantis separated, or it is possible to follow to an extent at whichattachment to white reference substrate bd is growth of the stalk withease (growth rate of tomato seedling is approximately 1 cm/day).

In addition, white reference substrate bd is supported on stalk PT2 ofthe plant. Thereby, it is possible to easily dispose white referencesubstrate bd on a reverse side of the leaf without using another supportmember, and it is possible to follow to an extent of growth of the stalk(growth rate of tomato seedling is approximately 1 cm/day).

Although various embodiments are described above while referring to thedrawings, needless to say, the present disclosure is not limited to theexamples. According to a person skilled in the art, within the scopewhich is set forth in the claims, it is obvious that it is possible toconceive of various modified examples and correction examples, andtherein is naturally understood as belonging to the technical scope ofthe present disclosure.

The present disclosure is able to set various products in which a dryingprocess is provided in a manufacturing process as the measurement targetother than the leaf of the plant that is set as the measurement target.

For example, as one product in which the drying process is provided inthe manufacturing process, a flexible substrate and the like isconsidered. When the flexible substrate is produced, in a heat dryingprocess, a reaction rate of a polyimide of a coating member, that is, animidization rate is important. The imidization rate is obtained bymeasuring the water content of the coating member, and calculating thewater content that is evaporated from the coating member. It is possibleto improve quality of the flexible substrate if the water contentevaluation apparatus of the present disclosure is applied to the heatdrying process of the flexible substrate.

In addition, as the product in which the drying process is provided inthe manufacturing process, ceramics, a wall of a building, nori seaweed,wakame seaweed, dry matter such as dried squid, a confection, paper, andthe like are given. In the respective drying process, if applied to takeadvantage of the water content evaluation apparatus of the presentdisclosure, the water content of the product is as small as possible, oran adequate water content, however it is possible to measure whether ornot there is a state in which unevenness is slight, and it is possibleto improve quality of the product.

What is claimed is:
 1. A water content evaluation apparatus whichevaluates water content of a part of an object, the water contentevaluation apparatus comprising: a first light source which radiates alaser reference beam of a first wavelength toward the object atirradiation positions of the object, the laser reference beam of thefirst wavelength not being absorbed by water; a second light sourcewhich radiates a laser measuring beam of a second wavelength toward theobject at the irradiation positions of the object, the laser measuringbeam of the second wavelength being absorbed by water; and a controllerthat executes instructions, the instructions, when executed by thecontroller, causing the controller to perform operations including:calculating water content at each of the irradiation positions of theobject based on a first reflection light of the laser reference beamthat is reflected at all the irradiation positions of the object and asecond reflection light of the laser measuring beam that is reflected atall the irradiation positions of the object; and outputting irradiationpositions of the object in which the water content is equal to or largerthan at least one predetermined threshold level.
 2. The water contentevaluation apparatus of claim 1, wherein one of the at least onepredetermined threshold level is a base threshold level which indicatesthe water content and identifies a shape of the object.
 3. The watercontent evaluation apparatus of claim 2, wherein the operations furtherincluding: acquiring a visible light image of the object; andcalculating the base threshold level using the visible light image ofthe object.
 4. The water content evaluation apparatus of claim 1,wherein the operations further include: outputting at least oneinvisible light image of the part of the object.
 5. The water contentevaluation apparatus of claim 4, wherein each of the irradiationsposition corresponds to a pixel of a predetermined number in the atleast one invisible light image.
 6. The water content evaluationapparatus of claim 1, wherein the first light source radiates a nearinfrared laser reference beam as the laser reference beam, and thesecond light source radiates a near infrared laser measuring beam as thelaser measuring beam.
 7. The water content evaluation apparatus of claim1, wherein the controller is a processor.
 8. The water contentevaluation apparatus of claim 1, wherein the object includes asubstrate.
 9. The water content evaluation apparatus of claim 1, whereinthe object includes a material of a building.
 10. The water contentevaluation apparatus of claim 1, wherein, before the water content iscalculated at each of the irradiation positions of the object, theobject is subject to a drying process.
 11. A water content evaluationapparatus, comprising: a first light source which radiates a laserreference beam of a first wavelength toward irradiation positions whichare included in a part of an object that is set as an evaluation target,a background material covering a back surface of the part of the object,the laser reference beam of the first wavelength not being absorbed bywater; a second light source which radiates a laser measuring beam of asecond wavelength toward the irradiation positions, the laser measuringbeam of the second wavelength being absorbed by water; a controller thatexecutes instructions, the instructions, when executed by thecontroller, causing the controller to perform operations including:identifying the part of the object that is set as the evaluation targetbased on a first reflection light of the laser reference beam that isreflected at the irradiation positions of the part of the object and asecond reflection light of the laser measuring beam that is reflected atthe irradiation positions of the part of the object; calculating watercontent of the part of the object that is set as the evaluation targetat each of the irradiation positions of the object based on the firstreflection light of the laser reference beam that is reflected at allthe irradiation positions of the part of the object and the secondreflection light of the laser measuring beam that is reflected at allthe irradiation positions of the part of the object; and outputtingirradiation positions of the object in which the water content is equalto or larger than at least one predetermined threshold level.
 12. Thewater content evaluation apparatus of claim 11, wherein the first lightsource radiates a near infrared laser reference beam as the laserreference beam, and the second light source radiates a near infraredlaser measuring beam as the laser measuring beam.
 13. The water contentevaluation apparatus of claim 11, wherein the controller is a processor.14. The water content evaluation apparatus of claim 11, wherein theobject includes a substrate.
 15. The water content evaluation apparatusof claim 11, wherein the object includes a material of a building. 16.The water content evaluation apparatus of claim 11, wherein, before thewater content of the part of the object is calculated, the object issubject to a drying process.
 17. A water content evaluation method for awater content evaluation apparatus, the water content evaluation methodcomprising: causing a first light source to radiate a laser referencebeam of a first wavelength toward an object at irradiation positions ofthe object, the laser reference beam of the first wavelength not beingabsorbed by water; causing a second light source to radiate a lasermeasuring beam of a second wavelength toward the object at theirradiation positions of the object, the laser measuring beam of thesecond wavelength being absorbed by water; calculating, by a controller,water content of the object at each of the irradiation positions of theobject based on a first reflection light of the laser reference beamthat is reflected at all the irradiation positions of the object and asecond reflection light of the laser measuring beam that is reflected atall the irradiation positions of the object; and outputting irradiationpositions of the object in which the water content is equal to or largerthan at least one predetermined threshold level.
 18. The water contentevaluation method of claim 17, wherein the first light source radiates anear infrared laser reference beam as the laser reference beam, and thesecond light source radiates a near infrared laser measuring beam as thelaser measuring beam.
 19. A water content evaluation method for a watercontent evaluation apparatus, the water content evaluation apparatusevaluating water content of a part of an object, the water contentevaluation method comprising: covering a back surface of the part of theobject with a background material, the part of the object being set asan evaluation target of the water content evaluation apparatus; causinga first light source to radiate a laser reference beam of a firstwavelength toward irradiation positions which comprise the part of theobject that is set as the evaluation target and the background material,the laser reference beam of the first wavelength not being absorbed bywater; causing a second light source to radiate a laser measuring beamof a second wavelength toward the irradiation positions, the lasermeasuring beam of the second wavelength being absorbed by water;identifying, by a controller, the part of the object that is set as theevaluation target based on a first reflection light of the laserreference beam that is reflected at the irradiation positions of thepart of the object and a second reflection light of the laser measuringbeam that is reflected at the irradiation positions of the part of theobject; calculating water content of the part of the object that is setas the evaluation target at each of the irradiation positions of theobject based on the first reflection light of the laser reference beamthat is reflected at all the irradiation positions of the part of theobject and the second reflection light of the laser measuring beam thatis reflected at all the irradiation positions of the part of the object;and outputting irradiation positions of the object in which the watercontent is equal to or larger than at least one predetermined thresholdlevel.
 20. The water content evaluation method of claim 19, wherein areflection intensity rate is calculated at each of the irradiationpositions that is irradiated with the laser reference beam and the lasermeasuring beam based on a first rate of a first reflection intensity ofthe laser reference beam and a second rate of a second reflectionintensity of the laser measuring beam, and the irradiation positions atwhich the calculated reflection intensity rate exceeds a threshold levelare set as the part of the object that is the evaluation target.
 21. Thewater content evaluation method of claim 20, wherein the thresholdlevel, corresponding to a cumulative frequency of the reflectionintensity rate, is obtained to include a same pixel number as anoccupied pixel number of a specific color of the part of the object thatis the evaluation target in a visible light image of the irradiationarea, the visible light image being imaged by a visible light camera.22. The water content evaluation method of claim 20, wherein anirradiation position at which the calculated reflection intensity rateis the threshold level or less is set as outside the evaluation targetof the water content evaluation apparatus.
 23. The water contentevaluation method of claim 19, wherein the part of the object that isset as the evaluation target is a substrate or dried matter.
 24. Thewater content evaluation method of claim 19, wherein the first lightsource radiates a near infrared laser reference beam as the laserreference beam, and the second light source radiates a near infraredlaser measuring beam as the laser measuring beam.